Historically, dental brackets have been quite easy to remove. That is, metal brackets which are generally bonded to a set of teeth have been removed through the use of dental pliers. After the removal of the archwire from each bracket, the orthodontist merely needed to pry the brackets, as a set, from the teeth. This required some bending of the bracket, but was not seen as a problem, due to the ease of removal. The orthodontist was able to remove the entire set of brackets within a matter of minutes. The brackets, if not extensively damaged, would be repaired and autoclaved for reuse. If beyond repair, the brackets would simply be discarded.
In recent years there has been an increase in the use of ceramic and sapphire brackets. These brackets are generally formed from a fired ceramic or sapphire material, and must be bonded to the tooth. This bonding allows each tooth to individually support a bracket, and the archwire strung through the set of brackets constantly urges the teeth into proper position in the mouth.
Removal of these ceramic and sapphire brackets, however, has proved quite difficult. Early techniques for removal included the prying of the individual dental brackets from the teeth. This posed a significant number of problems. First, the adhesive bonding strength caused the dental bracket to remain on the tooth face long enough so that a torque was transmitted to the root of the tooth. This frequently caused pain to the patient. Second, often the bonding strength of the adhesive was stronger than the shear strength of the bracket. When the bracket was removed by the prying method, the adhesive would often cause part of the bracket to remain on the tooth face. The rest of the bracket would shatter in the patient's mouth. This set of circumstances could prove quite trying. The chips of the dental bracket were usually dispersed, and the part of the dental bracket remaining on the tooth would need to be filed from the tooth face by a diamond-edged wheel.
Diamond cutting provided its own problems. First, many orthodontists are not adequately skilled in the use of a diamond cutting wheel. Second, this procedure can be quite tedious. Without a steady hand, there is the possibility of removal of the dental enamel along with the pieces of bracket and the bonding adhesive.
The final problem caused by prying of the dental brackets was that it could be extremely time consuming. Each tooth could take up to five minutes or more to have the bracket pried and then cleaned. This procedure could take up to one hour for an entire set of brackets, which is considered excessive both by patients and orthodontists.
Attempts were made to change the procedure of removal of dental brackets by the use of heat on the bracket. The early work of Sheridan, which culminated in U.S. Pat. No. 4,455,138, granted Jun. 19, 1984, demonstrated that with the application of heat to the dental bracket, the adhesive bonding the bracket to the tooth face would be loosened. The bracket could then be more easily pulled from the tooth face with a smaller prying force. This would allow quicker and more complete removal of the dental bracket without the need for prying.
The Sheridan device, however, also had significant drawbacks, much like the drawbacks encountered using the prying method. Because there was no control over the amount of force applied by the orthodontist, this force could vary from orthodontist to orthodontist. Thus, even though the bracket was being heated, the orthodontist could pull the bracket in anticipation of the loosening of the adhesive from the bracket. Again, this could potentially cause great pain. It also did not prevent the over-eager orthodontist from cracking or shattering the dental bracket before there was a chance to apply heat to loosen the adhesive.
Also, the Sheridan method had another significant drawback; the pulling force could not be directionally controlled. That is, the pulling force had no corresponding reaction force into the tooth face. Therefore, the orthodontist could twist or pry the tooth and exert a torque on the tooth face. In addition, the orthodontist could pull the tooth in any direction, creating shear on the tooth. This was potentially painful to the patient, and also enhanced the probability of shattering the bracket.